DETERMINATION OF THE WETTED OUTER SURFACE OF A WATER-SPRAYED FINNED-TUBES AIR-COOLED CONDENSER: A CASE OF A SPRAY NORMAL TO THE IMPACT AREA

Spraying water upstream of an air-cooled condenser allows to reduce the temperature of the inlet air flow and to obtain additional heat transfer gains when the water droplets impinge on the condenser outer walls. It is therefore a very effective method for improving the energetic performance of refrigeration systems. In this work, a prediction model of the wetted outer surface, well suited to finned-tubes air-cooled condensers and based on purely geometric arguments, is investigated. The wetted outer surface is expressed, in case of a spray normal to the impact area, as a function of the nozzle-condenser parameters. It is found that the condenser wetted outer surface increases with the spray angle, the spray-wall distance and the collected water flow rate. On the other hand, when the latter reaches a value of 0.009kg.s-1, the wetted area no longer increases with the collected water flow and becomes a constant at 0.07m2. It is also found that the condenser wetted outer surface is always greater with finned-tubes than with smooth tubes.